Phoma herbarum as a new gibberellin-producing and plant growth-promoting fungus

Endophytic fungi are known for the production of valuable metabolites, but information on the gibberellin production capacity of this group is limited. We isolated 9 endophytic fungi from the roots of salt-stressed soybean plants and screened them on waito-c rice, in order to identify plant growth promoting fungal strains. The fungal isolate TK-2-4 gave maximum plant length (20.35 cm) promotion in comparison with wild-type Gibberella fujikuroi (19.5 cm). In a separate experiment, bioassay of TK-2-4 promoted plant length and biomass of soybean cultivar Taegwangkong. The TK-2-4 culture filtrate was analyzed for the presence of gibberellins, and it was found that all physiologically active gibberellins, especially GA₄ and GA₇, were present in higher amounts (GA₁, 0.11 ng/ml; GA₃, 2.91 ng/ml; GA ₄, 3.21 ng/ml; and GA₇, 1.4 ng/ml) in conjunction with physiologically inactive GA₉ (0.05 ng/ml), GA₁₂ (0.23 ng/ ml), GA₁₅ (0.42 ng/ml), GA₁₉ (0.53 ng/ml), and GA ₂₀ (0.06 ng/ml). The fungal isolate TK-2-4 was later identified as a new strain of Phoma herbarum, through the phylogenetic analysis of 28S rDNA sequence.